The invention concerns a container folded from a sealable cardboard blank, in particular a food serving tray having a rectangular bottom, four folded sides each joined by the folding over of two essentially triangular corner regions, and a border flange parallel to the bottom of the border flange formed by four border strips joined to the sides by fold lines.
In a known container of this type, disclosed for example in German OS-25 45 410, two opposing border strips defining the border flange are in the form of a single layer, while the two other border strips of the border flange are in the form of three layers. The free outer edges of the border strips face outwardly, i.e,, are exposed to the outside containers of this type are not uniformly stable due to the uneven border flange and cannot be used in all cases. Containers of this type are stable enough to be further transported only after adhesive bonding or sealing.
From U.S. Pat. No. 4,199,097 there is known a folded container, not of this generic type, with arching external walls contiguous with each other. The container has a circumferential two-layer border flange which, however, is not parallel to the bottom. The cut edge is oriented toward the inner reversed edge of the border flange and is not exposed to the outside. In order to make possible the folding of the two-layer border flange in the arched areas, a plurality of conical, indented tabs is provided in the outer edge part of the border flange, which permits folding into a rounded shape. Containers of this type may be made of a thinner and thus less expensive material.
From European Patent 022 139, there is known a folded container with a border flange disposed parallel to the rectangular bottom. Two opposing border strips are equipped in the area of their corners with projections acting in the manner of hooks which, after the folding step grip the corners under the two adjacent border strips of the border flanges. The folded container is provided in this manner with a certain structural rigidity which, even prior to sealing, makes possible the safe transport of the folded container to other processing stations. However, the border flange has only one layer. It is, therefore, not possible to use a relatively thin initial material.
It is an object of the invention to develop a container of the afore-mentioned type at a low cost so that it may be made from a thin initial material, but which is provided with adequate cohesion and rigidity after folding and prior to sealing.